diff options
Diffstat (limited to 'lib/assoc_array.c')
| -rw-r--r-- | lib/assoc_array.c | 1746 |
1 files changed, 0 insertions, 1746 deletions
diff --git a/lib/assoc_array.c b/lib/assoc_array.c deleted file mode 100644 index 17edeaf..0000000 --- a/lib/assoc_array.c +++ /dev/null @@ -1,1746 +0,0 @@ -/* Generic associative array implementation. - * - * See Documentation/assoc_array.txt for information. - * - * Copyright (C) 2013 Red Hat, Inc. All Rights Reserved. - * Written by David Howells (dhowells@redhat.com) - * - * This program is free software; you can redistribute it and/or - * modify it under the terms of the GNU General Public Licence - * as published by the Free Software Foundation; either version - * 2 of the Licence, or (at your option) any later version. - */ -//#define DEBUG -#include <linux/slab.h> -#include <linux/err.h> -#include <linux/assoc_array_priv.h> - -/* - * Iterate over an associative array. The caller must hold the RCU read lock - * or better. - */ -static int assoc_array_subtree_iterate(const struct assoc_array_ptr *root, - const struct assoc_array_ptr *stop, - int (*iterator)(const void *leaf, - void *iterator_data), - void *iterator_data) -{ - const struct assoc_array_shortcut *shortcut; - const struct assoc_array_node *node; - const struct assoc_array_ptr *cursor, *ptr, *parent; - unsigned long has_meta; - int slot, ret; - - cursor = root; - -begin_node: - if (assoc_array_ptr_is_shortcut(cursor)) { - /* Descend through a shortcut */ - shortcut = assoc_array_ptr_to_shortcut(cursor); - smp_read_barrier_depends(); - cursor = ACCESS_ONCE(shortcut->next_node); - } - - node = assoc_array_ptr_to_node(cursor); - smp_read_barrier_depends(); - slot = 0; - - /* We perform two passes of each node. - * - * The first pass does all the leaves in this node. This means we - * don't miss any leaves if the node is split up by insertion whilst - * we're iterating over the branches rooted here (we may, however, see - * some leaves twice). - */ - has_meta = 0; - for (; slot < ASSOC_ARRAY_FAN_OUT; slot++) { - ptr = ACCESS_ONCE(node->slots[slot]); - has_meta |= (unsigned long)ptr; - if (ptr && assoc_array_ptr_is_leaf(ptr)) { - /* We need a barrier between the read of the pointer - * and dereferencing the pointer - but only if we are - * actually going to dereference it. - */ - smp_read_barrier_depends(); - - /* Invoke the callback */ - ret = iterator(assoc_array_ptr_to_leaf(ptr), - iterator_data); - if (ret) - return ret; - } - } - - /* The second pass attends to all the metadata pointers. If we follow - * one of these we may find that we don't come back here, but rather go - * back to a replacement node with the leaves in a different layout. - * - * We are guaranteed to make progress, however, as the slot number for - * a particular portion of the key space cannot change - and we - * continue at the back pointer + 1. - */ - if (!(has_meta & ASSOC_ARRAY_PTR_META_TYPE)) - goto finished_node; - slot = 0; - -continue_node: - node = assoc_array_ptr_to_node(cursor); - smp_read_barrier_depends(); - - for (; slot < ASSOC_ARRAY_FAN_OUT; slot++) { - ptr = ACCESS_ONCE(node->slots[slot]); - if (assoc_array_ptr_is_meta(ptr)) { - cursor = ptr; - goto begin_node; - } - } - -finished_node: - /* Move up to the parent (may need to skip back over a shortcut) */ - parent = ACCESS_ONCE(node->back_pointer); - slot = node->parent_slot; - if (parent == stop) - return 0; - - if (assoc_array_ptr_is_shortcut(parent)) { - shortcut = assoc_array_ptr_to_shortcut(parent); - smp_read_barrier_depends(); - cursor = parent; - parent = ACCESS_ONCE(shortcut->back_pointer); - slot = shortcut->parent_slot; - if (parent == stop) - return 0; - } - - /* Ascend to next slot in parent node */ - cursor = parent; - slot++; - goto continue_node; -} - -/** - * assoc_array_iterate - Pass all objects in the array to a callback - * @array: The array to iterate over. - * @iterator: The callback function. - * @iterator_data: Private data for the callback function. - * - * Iterate over all the objects in an associative array. Each one will be - * presented to the iterator function. - * - * If the array is being modified concurrently with the iteration then it is - * possible that some objects in the array will be passed to the iterator - * callback more than once - though every object should be passed at least - * once. If this is undesirable then the caller must lock against modification - * for the duration of this function. - * - * The function will return 0 if no objects were in the array or else it will - * return the result of the last iterator function called. Iteration stops - * immediately if any call to the iteration function results in a non-zero - * return. - * - * The caller should hold the RCU read lock or better if concurrent - * modification is possible. - */ -int assoc_array_iterate(const struct assoc_array *array, - int (*iterator)(const void *object, - void *iterator_data), - void *iterator_data) -{ - struct assoc_array_ptr *root = ACCESS_ONCE(array->root); - - if (!root) - return 0; - return assoc_array_subtree_iterate(root, NULL, iterator, iterator_data); -} - -enum assoc_array_walk_status { - assoc_array_walk_tree_empty, - assoc_array_walk_found_terminal_node, - assoc_array_walk_found_wrong_shortcut, -} status; - -struct assoc_array_walk_result { - struct { - struct assoc_array_node *node; /* Node in which leaf might be found */ - int level; - int slot; - } terminal_node; - struct { - struct assoc_array_shortcut *shortcut; - int level; - int sc_level; - unsigned long sc_segments; - unsigned long dissimilarity; - } wrong_shortcut; -}; - -/* - * Navigate through the internal tree looking for the closest node to the key. - */ -static enum assoc_array_walk_status -assoc_array_walk(const struct assoc_array *array, - const struct assoc_array_ops *ops, - const void *index_key, - struct assoc_array_walk_result *result) -{ - struct assoc_array_shortcut *shortcut; - struct assoc_array_node *node; - struct assoc_array_ptr *cursor, *ptr; - unsigned long sc_segments, dissimilarity; - unsigned long segments; - int level, sc_level, next_sc_level; - int slot; - - pr_devel("-->%s()\n", __func__); - - cursor = ACCESS_ONCE(array->root); - if (!cursor) - return assoc_array_walk_tree_empty; - - level = 0; - - /* Use segments from the key for the new leaf to navigate through the - * internal tree, skipping through nodes and shortcuts that are on - * route to the destination. Eventually we'll come to a slot that is - * either empty or contains a leaf at which point we've found a node in - * which the leaf we're looking for might be found or into which it - * should be inserted. - */ -jumped: - segments = ops->get_key_chunk(index_key, level); - pr_devel("segments[%d]: %lx\n", level, segments); - - if (assoc_array_ptr_is_shortcut(cursor)) - goto follow_shortcut; - -consider_node: - node = assoc_array_ptr_to_node(cursor); - smp_read_barrier_depends(); - - slot = segments >> (level & ASSOC_ARRAY_KEY_CHUNK_MASK); - slot &= ASSOC_ARRAY_FAN_MASK; - ptr = ACCESS_ONCE(node->slots[slot]); - - pr_devel("consider slot %x [ix=%d type=%lu]\n", - slot, level, (unsigned long)ptr & 3); - - if (!assoc_array_ptr_is_meta(ptr)) { - /* The node doesn't have a node/shortcut pointer in the slot - * corresponding to the index key that we have to follow. - */ - result->terminal_node.node = node; - result->terminal_node.level = level; - result->terminal_node.slot = slot; - pr_devel("<--%s() = terminal_node\n", __func__); - return assoc_array_walk_found_terminal_node; - } - - if (assoc_array_ptr_is_node(ptr)) { - /* There is a pointer to a node in the slot corresponding to - * this index key segment, so we need to follow it. - */ - cursor = ptr; - level += ASSOC_ARRAY_LEVEL_STEP; - if ((level & ASSOC_ARRAY_KEY_CHUNK_MASK) != 0) - goto consider_node; - goto jumped; - } - - /* There is a shortcut in the slot corresponding to the index key - * segment. We follow the shortcut if its partial index key matches - * this leaf's. Otherwise we need to split the shortcut. - */ - cursor = ptr; -follow_shortcut: - shortcut = assoc_array_ptr_to_shortcut(cursor); - smp_read_barrier_depends(); - pr_devel("shortcut to %d\n", shortcut->skip_to_level); - sc_level = level + ASSOC_ARRAY_LEVEL_STEP; - BUG_ON(sc_level > shortcut->skip_to_level); - - do { - /* Check the leaf against the shortcut's index key a word at a - * time, trimming the final word (the shortcut stores the index - * key completely from the root to the shortcut's target). - */ - if ((sc_level & ASSOC_ARRAY_KEY_CHUNK_MASK) == 0) - segments = ops->get_key_chunk(index_key, sc_level); - - sc_segments = shortcut->index_key[sc_level >> ASSOC_ARRAY_KEY_CHUNK_SHIFT]; - dissimilarity = segments ^ sc_segments; - - if (round_up(sc_level, ASSOC_ARRAY_KEY_CHUNK_SIZE) > shortcut->skip_to_level) { - /* Trim segments that are beyond the shortcut */ - int shift = shortcut->skip_to_level & ASSOC_ARRAY_KEY_CHUNK_MASK; - dissimilarity &= ~(ULONG_MAX << shift); - next_sc_level = shortcut->skip_to_level; - } else { - next_sc_level = sc_level + ASSOC_ARRAY_KEY_CHUNK_SIZE; - next_sc_level = round_down(next_sc_level, ASSOC_ARRAY_KEY_CHUNK_SIZE); - } - - if (dissimilarity != 0) { - /* This shortcut points elsewhere */ - result->wrong_shortcut.shortcut = shortcut; - result->wrong_shortcut.level = level; - result->wrong_shortcut.sc_level = sc_level; - result->wrong_shortcut.sc_segments = sc_segments; - result->wrong_shortcut.dissimilarity = dissimilarity; - return assoc_array_walk_found_wrong_shortcut; - } - - sc_level = next_sc_level; - } while (sc_level < shortcut->skip_to_level); - - /* The shortcut matches the leaf's index to this point. */ - cursor = ACCESS_ONCE(shortcut->next_node); - if (((level ^ sc_level) & ~ASSOC_ARRAY_KEY_CHUNK_MASK) != 0) { - level = sc_level; - goto jumped; - } else { - level = sc_level; - goto consider_node; - } -} - -/** - * assoc_array_find - Find an object by index key - * @array: The associative array to search. - * @ops: The operations to use. - * @index_key: The key to the object. - * - * Find an object in an associative array by walking through the internal tree - * to the node that should contain the object and then searching the leaves - * there. NULL is returned if the requested object was not found in the array. - * - * The caller must hold the RCU read lock or better. - */ -void *assoc_array_find(const struct assoc_array *array, - const struct assoc_array_ops *ops, - const void *index_key) -{ - struct assoc_array_walk_result result; - const struct assoc_array_node *node; - const struct assoc_array_ptr *ptr; - const void *leaf; - int slot; - - if (assoc_array_walk(array, ops, index_key, &result) != - assoc_array_walk_found_terminal_node) - return NULL; - - node = result.terminal_node.node; - smp_read_barrier_depends(); - - /* If the target key is available to us, it's has to be pointed to by - * the terminal node. - */ - for (slot = 0; slot < ASSOC_ARRAY_FAN_OUT; slot++) { - ptr = ACCESS_ONCE(node->slots[slot]); - if (ptr && assoc_array_ptr_is_leaf(ptr)) { - /* We need a barrier between the read of the pointer - * and dereferencing the pointer - but only if we are - * actually going to dereference it. - */ - leaf = assoc_array_ptr_to_leaf(ptr); - smp_read_barrier_depends(); - if (ops->compare_object(leaf, index_key)) - return (void *)leaf; - } - } - - return NULL; -} - -/* - * Destructively iterate over an associative array. The caller must prevent - * other simultaneous accesses. - */ -static void assoc_array_destroy_subtree(struct assoc_array_ptr *root, - const struct assoc_array_ops *ops) -{ - struct assoc_array_shortcut *shortcut; - struct assoc_array_node *node; - struct assoc_array_ptr *cursor, *parent = NULL; - int slot = -1; - - pr_devel("-->%s()\n", __func__); - - cursor = root; - if (!cursor) { - pr_devel("empty\n"); - return; - } - -move_to_meta: - if (assoc_array_ptr_is_shortcut(cursor)) { - /* Descend through a shortcut */ - pr_devel("[%d] shortcut\n", slot); - BUG_ON(!assoc_array_ptr_is_shortcut(cursor)); - shortcut = assoc_array_ptr_to_shortcut(cursor); - BUG_ON(shortcut->back_pointer != parent); - BUG_ON(slot != -1 && shortcut->parent_slot != slot); - parent = cursor; - cursor = shortcut->next_node; - slot = -1; - BUG_ON(!assoc_array_ptr_is_node(cursor)); - } - - pr_devel("[%d] node\n", slot); - node = assoc_array_ptr_to_node(cursor); - BUG_ON(node->back_pointer != parent); - BUG_ON(slot != -1 && node->parent_slot != slot); - slot = 0; - -continue_node: - pr_devel("Node %p [back=%p]\n", node, node->back_pointer); - for (; slot < ASSOC_ARRAY_FAN_OUT; slot++) { - struct assoc_array_ptr *ptr = node->slots[slot]; - if (!ptr) - continue; - if (assoc_array_ptr_is_meta(ptr)) { - parent = cursor; - cursor = ptr; - goto move_to_meta; - } - - if (ops) { - pr_devel("[%d] free leaf\n", slot); - ops->free_object(assoc_array_ptr_to_leaf(ptr)); - } - } - - parent = node->back_pointer; - slot = node->parent_slot; - pr_devel("free node\n"); - kfree(node); - if (!parent) - return; /* Done */ - - /* Move back up to the parent (may need to free a shortcut on - * the way up) */ - if (assoc_array_ptr_is_shortcut(parent)) { - shortcut = assoc_array_ptr_to_shortcut(parent); - BUG_ON(shortcut->next_node != cursor); - cursor = parent; - parent = shortcut->back_pointer; - slot = shortcut->parent_slot; - pr_devel("free shortcut\n"); - kfree(shortcut); - if (!parent) - return; - - BUG_ON(!assoc_array_ptr_is_node(parent)); - } - - /* Ascend to next slot in parent node */ - pr_devel("ascend to %p[%d]\n", parent, slot); - cursor = parent; - node = assoc_array_ptr_to_node(cursor); - slot++; - goto continue_node; -} - -/** - * assoc_array_destroy - Destroy an associative array - * @array: The array to destroy. - * @ops: The operations to use. - * - * Discard all metadata and free all objects in an associative array. The - * array will be empty and ready to use again upon completion. This function - * cannot fail. - * - * The caller must prevent all other accesses whilst this takes place as no - * attempt is made to adjust pointers gracefully to permit RCU readlock-holding - * accesses to continue. On the other hand, no memory allocation is required. - */ -void assoc_array_destroy(struct assoc_array *array, - const struct assoc_array_ops *ops) -{ - assoc_array_destroy_subtree(array->root, ops); - array->root = NULL; -} - -/* - * Handle insertion into an empty tree. - */ -static bool assoc_array_insert_in_empty_tree(struct assoc_array_edit *edit) -{ - struct assoc_array_node *new_n0; - - pr_devel("-->%s()\n", __func__); - - new_n0 = kzalloc(sizeof(struct assoc_array_node), GFP_KERNEL); - if (!new_n0) - return false; - - edit->new_meta[0] = assoc_array_node_to_ptr(new_n0); - edit->leaf_p = &new_n0->slots[0]; - edit->adjust_count_on = new_n0; - edit->set[0].ptr = &edit->array->root; - edit->set[0].to = assoc_array_node_to_ptr(new_n0); - - pr_devel("<--%s() = ok [no root]\n", __func__); - return true; -} - -/* - * Handle insertion into a terminal node. - */ -static bool assoc_array_insert_into_terminal_node(struct assoc_array_edit *edit, - const struct assoc_array_ops *ops, - const void *index_key, - struct assoc_array_walk_result *result) -{ - struct assoc_array_shortcut *shortcut, *new_s0; - struct assoc_array_node *node, *new_n0, *new_n1, *side; - struct assoc_array_ptr *ptr; - unsigned long dissimilarity, base_seg, blank; - size_t keylen; - bool have_meta; - int level, diff; - int slot, next_slot, free_slot, i, j; - - node = result->terminal_node.node; - level = result->terminal_node.level; - edit->segment_cache[ASSOC_ARRAY_FAN_OUT] = result->terminal_node.slot; - - pr_devel("-->%s()\n", __func__); - - /* We arrived at a node which doesn't have an onward node or shortcut - * pointer that we have to follow. This means that (a) the leaf we - * want must go here (either by insertion or replacement) or (b) we - * need to split this node and insert in one of the fragments. - */ - free_slot = -1; - - /* Firstly, we have to check the leaves in this node to see if there's - * a matching one we should replace in place. - */ - for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) { - ptr = node->slots[i]; - if (!ptr) { - free_slot = i; - continue; - } - if (ops->compare_object(assoc_array_ptr_to_leaf(ptr), index_key)) { - pr_devel("replace in slot %d\n", i); - edit->leaf_p = &node->slots[i]; - edit->dead_leaf = node->slots[i]; - pr_devel("<--%s() = ok [replace]\n", __func__); - return true; - } - } - - /* If there is a free slot in this node then we can just insert the - * leaf here. - */ - if (free_slot >= 0) { - pr_devel("insert in free slot %d\n", free_slot); - edit->leaf_p = &node->slots[free_slot]; - edit->adjust_count_on = node; - pr_devel("<--%s() = ok [insert]\n", __func__); - return true; - } - - /* The node has no spare slots - so we're either going to have to split - * it or insert another node before it. - * - * Whatever, we're going to need at least two new nodes - so allocate - * those now. We may also need a new shortcut, but we deal with that - * when we need it. - */ - new_n0 = kzalloc(sizeof(struct assoc_array_node), GFP_KERNEL); - if (!new_n0) - return false; - edit->new_meta[0] = assoc_array_node_to_ptr(new_n0); - new_n1 = kzalloc(sizeof(struct assoc_array_node), GFP_KERNEL); - if (!new_n1) - return false; - edit->new_meta[1] = assoc_array_node_to_ptr(new_n1); - - /* We need to find out how similar the leaves are. */ - pr_devel("no spare slots\n"); - have_meta = false; - for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) { - ptr = node->slots[i]; - if (assoc_array_ptr_is_meta(ptr)) { - edit->segment_cache[i] = 0xff; - have_meta = true; - continue; - } - base_seg = ops->get_object_key_chunk( - assoc_array_ptr_to_leaf(ptr), level); - base_seg >>= level & ASSOC_ARRAY_KEY_CHUNK_MASK; - edit->segment_cache[i] = base_seg & ASSOC_ARRAY_FAN_MASK; - } - - if (have_meta) { - pr_devel("have meta\n"); - goto split_node; - } - - /* The node contains only leaves */ - dissimilarity = 0; - base_seg = edit->segment_cache[0]; - for (i = 1; i < ASSOC_ARRAY_FAN_OUT; i++) - dissimilarity |= edit->segment_cache[i] ^ base_seg; - - pr_devel("only leaves; dissimilarity=%lx\n", dissimilarity); - - if ((dissimilarity & ASSOC_ARRAY_FAN_MASK) == 0) { - /* The old leaves all cluster in the same slot. We will need - * to insert a shortcut if the new node wants to cluster with them. - */ - if ((edit->segment_cache[ASSOC_ARRAY_FAN_OUT] ^ base_seg) == 0) - goto all_leaves_cluster_together; - - /* Otherwise we can just insert a new node ahead of the old - * one. - */ - goto present_leaves_cluster_but_not_new_leaf; - } - -split_node: - pr_devel("split node\n"); - - /* We need to split the current node; we know that the node doesn't - * simply contain a full set of leaves that cluster together (it - * contains meta pointers and/or non-clustering leaves). - * - * We need to expel at least two leaves out of a set consisting of the - * leaves in the node and the new leaf. - * - * We need a new node (n0) to replace the current one and a new node to - * take the expelled nodes (n1). - */ - edit->set[0].to = assoc_array_node_to_ptr(new_n0); - new_n0->back_pointer = node->back_pointer; - new_n0->parent_slot = node->parent_slot; - new_n1->back_pointer = assoc_array_node_to_ptr(new_n0); - new_n1->parent_slot = -1; /* Need to calculate this */ - -do_split_node: - pr_devel("do_split_node\n"); - - new_n0->nr_leaves_on_branch = node->nr_leaves_on_branch; - new_n1->nr_leaves_on_branch = 0; - - /* Begin by finding two matching leaves. There have to be at least two - * that match - even if there are meta pointers - because any leaf that - * would match a slot with a meta pointer in it must be somewhere - * behind that meta pointer and cannot be here. Further, given N - * remaining leaf slots, we now have N+1 leaves to go in them. - */ - for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) { - slot = edit->segment_cache[i]; - if (slot != 0xff) - for (j = i + 1; j < ASSOC_ARRAY_FAN_OUT + 1; j++) - if (edit->segment_cache[j] == slot) - goto found_slot_for_multiple_occupancy; - } -found_slot_for_multiple_occupancy: - pr_devel("same slot: %x %x [%02x]\n", i, j, slot); - BUG_ON(i >= ASSOC_ARRAY_FAN_OUT); - BUG_ON(j >= ASSOC_ARRAY_FAN_OUT + 1); - BUG_ON(slot >= ASSOC_ARRAY_FAN_OUT); - - new_n1->parent_slot = slot; - - /* Metadata pointers cannot change slot */ - for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) - if (assoc_array_ptr_is_meta(node->slots[i])) - new_n0->slots[i] = node->slots[i]; - else - new_n0->slots[i] = NULL; - BUG_ON(new_n0->slots[slot] != NULL); - new_n0->slots[slot] = assoc_array_node_to_ptr(new_n1); - - /* Filter the leaf pointers between the new nodes */ - free_slot = -1; - next_slot = 0; - for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) { - if (assoc_array_ptr_is_meta(node->slots[i])) - continue; - if (edit->segment_cache[i] == slot) { - new_n1->slots[next_slot++] = node->slots[i]; - new_n1->nr_leaves_on_branch++; - } else { - do { - free_slot++; - } while (new_n0->slots[free_slot] != NULL); - new_n0->slots[free_slot] = node->slots[i]; - } - } - - pr_devel("filtered: f=%x n=%x\n", free_slot, next_slot); - - if (edit->segment_cache[ASSOC_ARRAY_FAN_OUT] != slot) { - do { - free_slot++; - } while (new_n0->slots[free_slot] != NULL); - edit->leaf_p = &new_n0->slots[free_slot]; - edit->adjust_count_on = new_n0; - } else { - edit->leaf_p = &new_n1->slots[next_slot++]; - edit->adjust_count_on = new_n1; - } - - BUG_ON(next_slot <= 1); - - edit->set_backpointers_to = assoc_array_node_to_ptr(new_n0); - for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) { - if (edit->segment_cache[i] == 0xff) { - ptr = node->slots[i]; - BUG_ON(assoc_array_ptr_is_leaf(ptr)); - if (assoc_array_ptr_is_node(ptr)) { - side = assoc_array_ptr_to_node(ptr); - edit->set_backpointers[i] = &side->back_pointer; - } else { - shortcut = assoc_array_ptr_to_shortcut(ptr); - edit->set_backpointers[i] = &shortcut->back_pointer; - } - } - } - - ptr = node->back_pointer; - if (!ptr) - edit->set[0].ptr = &edit->array->root; - else if (assoc_array_ptr_is_node(ptr)) - edit->set[0].ptr = &assoc_array_ptr_to_node(ptr)->slots[node->parent_slot]; - else - edit->set[0].ptr = &assoc_array_ptr_to_shortcut(ptr)->next_node; - edit->excised_meta[0] = assoc_array_node_to_ptr(node); - pr_devel("<--%s() = ok [split node]\n", __func__); - return true; - -present_leaves_cluster_but_not_new_leaf: - /* All the old leaves cluster in the same slot, but the new leaf wants - * to go into a different slot, so we create a new node to hold the new - * leaf and a pointer to a new node holding all the old leaves. - */ - pr_devel("present leaves cluster but not new leaf\n"); - - new_n0->back_pointer = node->back_pointer; - new_n0->parent_slot = node->parent_slot; - new_n0->nr_leaves_on_branch = node->nr_leaves_on_branch; - new_n1->back_pointer = assoc_array_node_to_ptr(new_n0); - new_n1->parent_slot = edit->segment_cache[0]; - new_n1->nr_leaves_on_branch = node->nr_leaves_on_branch; - edit->adjust_count_on = new_n0; - - for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) - new_n1->slots[i] = node->slots[i]; - - new_n0->slots[edit->segment_cache[0]] = assoc_array_node_to_ptr(new_n0); - edit->leaf_p = &new_n0->slots[edit->segment_cache[ASSOC_ARRAY_FAN_OUT]]; - - edit->set[0].ptr = &assoc_array_ptr_to_node(node->back_pointer)->slots[node->parent_slot]; - edit->set[0].to = assoc_array_node_to_ptr(new_n0); - edit->excised_meta[0] = assoc_array_node_to_ptr(node); - pr_devel("<--%s() = ok [insert node before]\n", __func__); - return true; - -all_leaves_cluster_together: - /* All the leaves, new and old, want to cluster together in this node - * in the same slot, so we have to replace this node with a shortcut to - * skip over the identical parts of the key and then place a pair of - * nodes, one inside the other, at the end of the shortcut and - * distribute the keys between them. - * - * Firstly we need to work out where the leaves start diverging as a - * bit position into their keys so that we know how big the shortcut - * needs to be. - * - * We only need to make a single pass of N of the N+1 leaves because if - * any keys differ between themselves at bit X then at least one of - * them must also differ with the base key at bit X or before. - */ - pr_devel("all leaves cluster together\n"); - diff = INT_MAX; - for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) { - int x = ops->diff_objects(assoc_array_ptr_to_leaf(edit->leaf), - assoc_array_ptr_to_leaf(node->slots[i])); - if (x < diff) { - BUG_ON(x < 0); - diff = x; - } - } - BUG_ON(diff == INT_MAX); - BUG_ON(diff < level + ASSOC_ARRAY_LEVEL_STEP); - - keylen = round_up(diff, ASSOC_ARRAY_KEY_CHUNK_SIZE); - keylen >>= ASSOC_ARRAY_KEY_CHUNK_SHIFT; - - new_s0 = kzalloc(sizeof(struct assoc_array_shortcut) + - keylen * sizeof(unsigned long), GFP_KERNEL); - if (!new_s0) - return false; - edit->new_meta[2] = assoc_array_shortcut_to_ptr(new_s0); - - edit->set[0].to = assoc_array_shortcut_to_ptr(new_s0); - new_s0->back_pointer = node->back_pointer; - new_s0->parent_slot = node->parent_slot; - new_s0->next_node = assoc_array_node_to_ptr(new_n0); - new_n0->back_pointer = assoc_array_shortcut_to_ptr(new_s0); - new_n0->parent_slot = 0; - new_n1->back_pointer = assoc_array_node_to_ptr(new_n0); - new_n1->parent_slot = -1; /* Need to calculate this */ - - new_s0->skip_to_level = level = diff & ~ASSOC_ARRAY_LEVEL_STEP_MASK; - pr_devel("skip_to_level = %d [diff %d]\n", level, diff); - BUG_ON(level <= 0); - - for (i = 0; i < keylen; i++) - new_s0->index_key[i] = - ops->get_key_chunk(index_key, i * ASSOC_ARRAY_KEY_CHUNK_SIZE); - - blank = ULONG_MAX << (level & ASSOC_ARRAY_KEY_CHUNK_MASK); - pr_devel("blank off [%zu] %d: %lx\n", keylen - 1, level, blank); - new_s0->index_key[keylen - 1] &= ~blank; - - /* This now reduces to a node splitting exercise for which we'll need - * to regenerate the disparity table. - */ - for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) { - ptr = node->slots[i]; - base_seg = ops->get_object_key_chunk(assoc_array_ptr_to_leaf(ptr), - level); - base_seg >>= level & ASSOC_ARRAY_KEY_CHUNK_MASK; - edit->segment_cache[i] = base_seg & ASSOC_ARRAY_FAN_MASK; - } - - base_seg = ops->get_key_chunk(index_key, level); - base_seg >>= level & ASSOC_ARRAY_KEY_CHUNK_MASK; - edit->segment_cache[ASSOC_ARRAY_FAN_OUT] = base_seg & ASSOC_ARRAY_FAN_MASK; - goto do_split_node; -} - -/* - * Handle insertion into the middle of a shortcut. - */ -static bool assoc_array_insert_mid_shortcut(struct assoc_array_edit *edit, - const struct assoc_array_ops *ops, - struct assoc_array_walk_result *result) -{ - struct assoc_array_shortcut *shortcut, *new_s0, *new_s1; - struct assoc_array_node *node, *new_n0, *side; - unsigned long sc_segments, dissimilarity, blank; - size_t keylen; - int level, sc_level, diff; - int sc_slot; - - shortcut = result->wrong_shortcut.shortcut; - level = result->wrong_shortcut.level; - sc_level = result->wrong_shortcut.sc_level; - sc_segments = result->wrong_shortcut.sc_segments; - dissimilarity = result->wrong_shortcut.dissimilarity; - - pr_devel("-->%s(ix=%d dis=%lx scix=%d)\n", - __func__, level, dissimilarity, sc_level); - - /* We need to split a shortcut and insert a node between the two - * pieces. Zero-length pieces will be dispensed with entirely. - * - * First of all, we need to find out in which level the first - * difference was. - */ - diff = __ffs(dissimilarity); - diff &= ~ASSOC_ARRAY_LEVEL_STEP_MASK; - diff += sc_level & ~ASSOC_ARRAY_KEY_CHUNK_MASK; - pr_devel("diff=%d\n", diff); - - if (!shortcut->back_pointer) { - edit->set[0].ptr = &edit->array->root; - } else if (assoc_array_ptr_is_node(shortcut->back_pointer)) { - node = assoc_array_ptr_to_node(shortcut->back_pointer); - edit->set[0].ptr = &node->slots[shortcut->parent_slot]; - } else { - BUG(); - } - - edit->excised_meta[0] = assoc_array_shortcut_to_ptr(shortcut); - - /* Create a new node now since we're going to need it anyway */ - new_n0 = kzalloc(sizeof(struct assoc_array_node), GFP_KERNEL); - if (!new_n0) - return false; - edit->new_meta[0] = assoc_array_node_to_ptr(new_n0); - edit->adjust_count_on = new_n0; - - /* Insert a new shortcut before the new node if this segment isn't of - * zero length - otherwise we just connect the new node directly to the - * parent. - */ - level += ASSOC_ARRAY_LEVEL_STEP; - if (diff > level) { - pr_devel("pre-shortcut %d...%d\n", level, diff); - keylen = round_up(diff, ASSOC_ARRAY_KEY_CHUNK_SIZE); - keylen >>= ASSOC_ARRAY_KEY_CHUNK_SHIFT; - - new_s0 = kzalloc(sizeof(struct assoc_array_shortcut) + - keylen * sizeof(unsigned long), GFP_KERNEL); - if (!new_s0) - return false; - edit->new_meta[1] = assoc_array_shortcut_to_ptr(new_s0); - edit->set[0].to = assoc_array_shortcut_to_ptr(new_s0); - new_s0->back_pointer = shortcut->back_pointer; - new_s0->parent_slot = shortcut->parent_slot; - new_s0->next_node = assoc_array_node_to_ptr(new_n0); - new_s0->skip_to_level = diff; - - new_n0->back_pointer = assoc_array_shortcut_to_ptr(new_s0); - new_n0->parent_slot = 0; - - memcpy(new_s0->index_key, shortcut->index_key, - keylen * sizeof(unsigned long)); - - blank = ULONG_MAX << (diff & ASSOC_ARRAY_KEY_CHUNK_MASK); - pr_devel("blank off [%zu] %d: %lx\n", keylen - 1, diff, blank); - new_s0->index_key[keylen - 1] &= ~blank; - } else { - pr_devel("no pre-shortcut\n"); - edit->set[0].to = assoc_array_node_to_ptr(new_n0); - new_n0->back_pointer = shortcut->back_pointer; - new_n0->parent_slot = shortcut->parent_slot; - } - - side = assoc_array_ptr_to_node(shortcut->next_node); - new_n0->nr_leaves_on_branch = side->nr_leaves_on_branch; - - /* We need to know which slot in the new node is going to take a - * metadata pointer. - */ - sc_slot = sc_segments >> (diff & ASSOC_ARRAY_KEY_CHUNK_MASK); - sc_slot &= ASSOC_ARRAY_FAN_MASK; - - pr_devel("new slot %lx >> %d -> %d\n", - sc_segments, diff & ASSOC_ARRAY_KEY_CHUNK_MASK, sc_slot); - - /* Determine whether we need to follow the new node with a replacement - * for the current shortcut. We could in theory reuse the current - * shortcut if its parent slot number doesn't change - but that's a - * 1-in-16 chance so not worth expending the code upon. - */ - level = diff + ASSOC_ARRAY_LEVEL_STEP; - if (level < shortcut->skip_to_level) { - pr_devel("post-shortcut %d...%d\n", level, shortcut->skip_to_level); - keylen = round_up(shortcut->skip_to_level, ASSOC_ARRAY_KEY_CHUNK_SIZE); - keylen >>= ASSOC_ARRAY_KEY_CHUNK_SHIFT; - - new_s1 = kzalloc(sizeof(struct assoc_array_shortcut) + - keylen * sizeof(unsigned long), GFP_KERNEL); - if (!new_s1) - return false; - edit->new_meta[2] = assoc_array_shortcut_to_ptr(new_s1); - - new_s1->back_pointer = assoc_array_node_to_ptr(new_n0); - new_s1->parent_slot = sc_slot; - new_s1->next_node = shortcut->next_node; - new_s1->skip_to_level = shortcut->skip_to_level; - - new_n0->slots[sc_slot] = assoc_array_shortcut_to_ptr(new_s1); - - memcpy(new_s1->index_key, shortcut->index_key, - keylen * sizeof(unsigned long)); - - edit->set[1].ptr = &side->back_pointer; - edit->set[1].to = assoc_array_shortcut_to_ptr(new_s1); - } else { - pr_devel("no post-shortcut\n"); - - /* We don't have to replace the pointed-to node as long as we - * use memory barriers to make sure the parent slot number is - * changed before the back pointer (the parent slot number is - * irrelevant to the old parent shortcut). - */ - new_n0->slots[sc_slot] = shortcut->next_node; - edit->set_parent_slot[0].p = &side->parent_slot; - edit->set_parent_slot[0].to = sc_slot; - edit->set[1].ptr = &side->back_pointer; - edit->set[1].to = assoc_array_node_to_ptr(new_n0); - } - - /* Install the new leaf in a spare slot in the new node. */ - if (sc_slot == 0) - edit->leaf_p = &new_n0->slots[1]; - else - edit->leaf_p = &new_n0->slots[0]; - - pr_devel("<--%s() = ok [split shortcut]\n", __func__); - return edit; -} - -/** - * assoc_array_insert - Script insertion of an object into an associative array - * @array: The array to insert into. - * @ops: The operations to use. - * @index_key: The key to insert at. - * @object: The object to insert. - * - * Precalculate and preallocate a script for the insertion or replacement of an - * object in an associative array. This results in an edit script that can - * either be applied or cancelled. - * - * The function returns a pointer to an edit script or -ENOMEM. - * - * The caller should lock against other modifications and must continue to hold - * the lock until assoc_array_apply_edit() has been called. - * - * Accesses to the tree may take place concurrently with this function, - * provided they hold the RCU read lock. - */ -struct assoc_array_edit *assoc_array_insert(struct assoc_array *array, - const struct assoc_array_ops *ops, - const void *index_key, - void *object) -{ - struct assoc_array_walk_result result; - struct assoc_array_edit *edit; - - pr_devel("-->%s()\n", __func__); - - /* The leaf pointer we're given must not have the bottom bit set as we - * use those for type-marking the pointer. NULL pointers are also not - * allowed as they indicate an empty slot but we have to allow them - * here as they can be updated later. - */ - BUG_ON(assoc_array_ptr_is_meta(object)); - - edit = kzalloc(sizeof(struct assoc_array_edit), GFP_KERNEL); - if (!edit) - return ERR_PTR(-ENOMEM); - edit->array = array; - edit->ops = ops; - edit->leaf = assoc_array_leaf_to_ptr(object); - edit->adjust_count_by = 1; - - switch (assoc_array_walk(array, ops, index_key, &result)) { - case assoc_array_walk_tree_empty: - /* Allocate a root node if there isn't one yet */ - if (!assoc_array_insert_in_empty_tree(edit)) - goto enomem; - return edit; - - case assoc_array_walk_found_terminal_node: - /* We found a node that doesn't have a node/shortcut pointer in - * the slot corresponding to the index key that we have to - * follow. - */ - if (!assoc_array_insert_into_terminal_node(edit, ops, index_key, - &result)) - goto enomem; - return edit; - - case assoc_array_walk_found_wrong_shortcut: - /* We found a shortcut that didn't match our key in a slot we - * needed to follow. - */ - if (!assoc_array_insert_mid_shortcut(edit, ops, &result)) - goto enomem; - return edit; - } - -enomem: - /* Clean up after an out of memory error */ - pr_devel("enomem\n"); - assoc_array_cancel_edit(edit); - return ERR_PTR(-ENOMEM); -} - -/** - * assoc_array_insert_set_object - Set the new object pointer in an edit script - * @edit: The edit script to modify. - * @object: The object pointer to set. - * - * Change the object to be inserted in an edit script. The object pointed to - * by the old object is not freed. This must be done prior to applying the - * script. - */ -void assoc_array_insert_set_object(struct assoc_array_edit *edit, void *object) -{ - BUG_ON(!object); - edit->leaf = assoc_array_leaf_to_ptr(object); -} - -struct assoc_array_delete_collapse_context { - struct assoc_array_node *node; - const void *skip_leaf; - int slot; -}; - -/* - * Subtree collapse to node iterator. - */ -static int assoc_array_delete_collapse_iterator(const void *leaf, - void *iterator_data) -{ - struct assoc_array_delete_collapse_context *collapse = iterator_data; - - if (leaf == collapse->skip_leaf) - return 0; - - BUG_ON(collapse->slot >= ASSOC_ARRAY_FAN_OUT); - - collapse->node->slots[collapse->slot++] = assoc_array_leaf_to_ptr(leaf); - return 0; -} - -/** - * assoc_array_delete - Script deletion of an object from an associative array - * @array: The array to search. - * @ops: The operations to use. - * @index_key: The key to the object. - * - * Precalculate and preallocate a script for the deletion of an object from an - * associative array. This results in an edit script that can either be - * applied or cancelled. - * - * The function returns a pointer to an edit script if the object was found, - * NULL if the object was not found or -ENOMEM. - * - * The caller should lock against other modifications and must continue to hold - * the lock until assoc_array_apply_edit() has been called. - * - * Accesses to the tree may take place concurrently with this function, - * provided they hold the RCU read lock. - */ -struct assoc_array_edit *assoc_array_delete(struct assoc_array *array, - const struct assoc_array_ops *ops, - const void *index_key) -{ - struct assoc_array_delete_collapse_context collapse; - struct assoc_array_walk_result result; - struct assoc_array_node *node, *new_n0; - struct assoc_array_edit *edit; - struct assoc_array_ptr *ptr; - bool has_meta; - int slot, i; - - pr_devel("-->%s()\n", __func__); - - edit = kzalloc(sizeof(struct assoc_array_edit), GFP_KERNEL); - if (!edit) - return ERR_PTR(-ENOMEM); - edit->array = array; - edit->ops = ops; - edit->adjust_count_by = -1; - - switch (assoc_array_walk(array, ops, index_key, &result)) { - case assoc_array_walk_found_terminal_node: - /* We found a node that should contain the leaf we've been - * asked to remove - *if* it's in the tree. - */ - pr_devel("terminal_node\n"); - node = result.terminal_node.node; - - for (slot = 0; slot < ASSOC_ARRAY_FAN_OUT; slot++) { - ptr = node->slots[slot]; - if (ptr && - assoc_array_ptr_is_leaf(ptr) && - ops->compare_object(assoc_array_ptr_to_leaf(ptr), - index_key)) - goto found_leaf; - } - case assoc_array_walk_tree_empty: - case assoc_array_walk_found_wrong_shortcut: - default: - assoc_array_cancel_edit(edit); - pr_devel("not found\n"); - return NULL; - } - -found_leaf: - BUG_ON(array->nr_leaves_on_tree <= 0); - - /* In the simplest form of deletion we just clear the slot and release - * the leaf after a suitable interval. - */ - edit->dead_leaf = node->slots[slot]; - edit->set[0].ptr = &node->slots[slot]; - edit->set[0].to = NULL; - edit->adjust_count_on = node; - - /* If that concludes erasure of the last leaf, then delete the entire - * internal array. - */ - if (array->nr_leaves_on_tree == 1) { - edit->set[1].ptr = &array->root; - edit->set[1].to = NULL; - edit->adjust_count_on = NULL; - edit->excised_subtree = array->root; - pr_devel("all gone\n"); - return edit; - } - - /* However, we'd also like to clear up some metadata blocks if we - * possibly can. - * - * We go for a simple algorithm of: if this node has FAN_OUT or fewer - * leaves in it, then attempt to collapse it - and attempt to - * recursively collapse up the tree. - * - * We could also try and collapse in partially filled subtrees to take - * up space in this node. - */ - if (node->nr_leaves_on_branch <= ASSOC_ARRAY_FAN_OUT + 1) { - struct assoc_array_node *parent, *grandparent; - struct assoc_array_ptr *ptr; - - /* First of all, we need to know if this node has metadata so - * that we don't try collapsing if all the leaves are already - * here. - */ - has_meta = false; - for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) { - ptr = node->slots[i]; - if (assoc_array_ptr_is_meta(ptr)) { - has_meta = true; - break; - } - } - - pr_devel("leaves: %ld [m=%d]\n", - node->nr_leaves_on_branch - 1, has_meta); - - /* Look further up the tree to see if we can collapse this node - * into a more proximal node too. - */ - parent = node; - collapse_up: - pr_devel("collapse subtree: %ld\n", parent->nr_leaves_on_branch); - - ptr = parent->back_pointer; - if (!ptr) - goto do_collapse; - if (assoc_array_ptr_is_shortcut(ptr)) { - struct assoc_array_shortcut *s = assoc_array_ptr_to_shortcut(ptr); - ptr = s->back_pointer; - if (!ptr) - goto do_collapse; - } - - grandparent = assoc_array_ptr_to_node(ptr); - if (grandparent->nr_leaves_on_branch <= ASSOC_ARRAY_FAN_OUT + 1) { - parent = grandparent; - goto collapse_up; - } - - do_collapse: - /* There's no point collapsing if the original node has no meta - * pointers to discard and if we didn't merge into one of that - * node's ancestry. - */ - if (has_meta || parent != node) { - node = parent; - - /* Create a new node to collapse into */ - new_n0 = kzalloc(sizeof(struct assoc_array_node), GFP_KERNEL); - if (!new_n0) - goto enomem; - edit->new_meta[0] = assoc_array_node_to_ptr(new_n0); - - new_n0->back_pointer = node->back_pointer; - new_n0->parent_slot = node->parent_slot; - new_n0->nr_leaves_on_branch = node->nr_leaves_on_branch; - edit->adjust_count_on = new_n0; - - collapse.node = new_n0; - collapse.skip_leaf = assoc_array_ptr_to_leaf(edit->dead_leaf); - collapse.slot = 0; - assoc_array_subtree_iterate(assoc_array_node_to_ptr(node), - node->back_pointer, - assoc_array_delete_collapse_iterator, - &collapse); - pr_devel("collapsed %d,%lu\n", collapse.slot, new_n0->nr_leaves_on_branch); - BUG_ON(collapse.slot != new_n0->nr_leaves_on_branch - 1); - - if (!node->back_pointer) { - edit->set[1].ptr = &array->root; - } else if (assoc_array_ptr_is_leaf(node->back_pointer)) { - BUG(); - } else if (assoc_array_ptr_is_node(node->back_pointer)) { - struct assoc_array_node *p = - assoc_array_ptr_to_node(node->back_pointer); - edit->set[1].ptr = &p->slots[node->parent_slot]; - } else if (assoc_array_ptr_is_shortcut(node->back_pointer)) { - struct assoc_array_shortcut *s = - assoc_array_ptr_to_shortcut(node->back_pointer); - edit->set[1].ptr = &s->next_node; - } - edit->set[1].to = assoc_array_node_to_ptr(new_n0); - edit->excised_subtree = assoc_array_node_to_ptr(node); - } - } - - return edit; - -enomem: - /* Clean up after an out of memory error */ - pr_devel("enomem\n"); - assoc_array_cancel_edit(edit); - return ERR_PTR(-ENOMEM); -} - -/** - * assoc_array_clear - Script deletion of all objects from an associative array - * @array: The array to clear. - * @ops: The operations to use. - * - * Precalculate and preallocate a script for the deletion of all the objects - * from an associative array. This results in an edit script that can either - * be applied or cancelled. - * - * The function returns a pointer to an edit script if there are objects to be - * deleted, NULL if there are no objects in the array or -ENOMEM. - * - * The caller should lock against other modifications and must continue to hold - * the lock until assoc_array_apply_edit() has been called. - * - * Accesses to the tree may take place concurrently with this function, - * provided they hold the RCU read lock. - */ -struct assoc_array_edit *assoc_array_clear(struct assoc_array *array, - const struct assoc_array_ops *ops) -{ - struct assoc_array_edit *edit; - - pr_devel("-->%s()\n", __func__); - - if (!array->root) - return NULL; - - edit = kzalloc(sizeof(struct assoc_array_edit), GFP_KERNEL); - if (!edit) - return ERR_PTR(-ENOMEM); - edit->array = array; - edit->ops = ops; - edit->set[1].ptr = &array->root; - edit->set[1].to = NULL; - edit->excised_subtree = array->root; - edit->ops_for_excised_subtree = ops; - pr_devel("all gone\n"); - return edit; -} - -/* - * Handle the deferred destruction after an applied edit. - */ -static void assoc_array_rcu_cleanup(struct rcu_head *head) -{ - struct assoc_array_edit *edit = - container_of(head, struct assoc_array_edit, rcu); - int i; - - pr_devel("-->%s()\n", __func__); - - if (edit->dead_leaf) - edit->ops->free_object(assoc_array_ptr_to_leaf(edit->dead_leaf)); - for (i = 0; i < ARRAY_SIZE(edit->excised_meta); i++) - if (edit->excised_meta[i]) - kfree(assoc_array_ptr_to_node(edit->excised_meta[i])); - - if (edit->excised_subtree) { - BUG_ON(assoc_array_ptr_is_leaf(edit->excised_subtree)); - if (assoc_array_ptr_is_node(edit->excised_subtree)) { - struct assoc_array_node *n = - assoc_array_ptr_to_node(edit->excised_subtree); - n->back_pointer = NULL; - } else { - struct assoc_array_shortcut *s = - assoc_array_ptr_to_shortcut(edit->excised_subtree); - s->back_pointer = NULL; - } - assoc_array_destroy_subtree(edit->excised_subtree, - edit->ops_for_excised_subtree); - } - - kfree(edit); -} - -/** - * assoc_array_apply_edit - Apply an edit script to an associative array - * @edit: The script to apply. - * - * Apply an edit script to an associative array to effect an insertion, - * deletion or clearance. As the edit script includes preallocated memory, - * this is guaranteed not to fail. - * - * The edit script, dead objects and dead metadata will be scheduled for - * destruction after an RCU grace period to permit those doing read-only - * accesses on the array to continue to do so under the RCU read lock whilst - * the edit is taking place. - */ -void assoc_array_apply_edit(struct assoc_array_edit *edit) -{ - struct assoc_array_shortcut *shortcut; - struct assoc_array_node *node; - struct assoc_array_ptr *ptr; - int i; - - pr_devel("-->%s()\n", __func__); - - smp_wmb(); - if (edit->leaf_p) - *edit->leaf_p = edit->leaf; - - smp_wmb(); - for (i = 0; i < ARRAY_SIZE(edit->set_parent_slot); i++) - if (edit->set_parent_slot[i].p) - *edit->set_parent_slot[i].p = edit->set_parent_slot[i].to; - - smp_wmb(); - for (i = 0; i < ARRAY_SIZE(edit->set_backpointers); i++) - if (edit->set_backpointers[i]) - *edit->set_backpointers[i] = edit->set_backpointers_to; - - smp_wmb(); - for (i = 0; i < ARRAY_SIZE(edit->set); i++) - if (edit->set[i].ptr) - *edit->set[i].ptr = edit->set[i].to; - - if (edit->array->root == NULL) { - edit->array->nr_leaves_on_tree = 0; - } else if (edit->adjust_count_on) { - node = edit->adjust_count_on; - for (;;) { - node->nr_leaves_on_branch += edit->adjust_count_by; - - ptr = node->back_pointer; - if (!ptr) - break; - if (assoc_array_ptr_is_shortcut(ptr)) { - shortcut = assoc_array_ptr_to_shortcut(ptr); - ptr = shortcut->back_pointer; - if (!ptr) - break; - } - BUG_ON(!assoc_array_ptr_is_node(ptr)); - node = assoc_array_ptr_to_node(ptr); - } - - edit->array->nr_leaves_on_tree += edit->adjust_count_by; - } - - call_rcu(&edit->rcu, assoc_array_rcu_cleanup); -} - -/** - * assoc_array_cancel_edit - Discard an edit script. - * @edit: The script to discard. - * - * Free an edit script and all the preallocated data it holds without making - * any changes to the associative array it was intended for. - * - * NOTE! In the case of an insertion script, this does _not_ release the leaf - * that was to be inserted. That is left to the caller. - */ -void assoc_array_cancel_edit(struct assoc_array_edit *edit) -{ - struct assoc_array_ptr *ptr; - int i; - - pr_devel("-->%s()\n", __func__); - - /* Clean up after an out of memory error */ - for (i = 0; i < ARRAY_SIZE(edit->new_meta); i++) { - ptr = edit->new_meta[i]; - if (ptr) { - if (assoc_array_ptr_is_node(ptr)) - kfree(assoc_array_ptr_to_node(ptr)); - else - kfree(assoc_array_ptr_to_shortcut(ptr)); - } - } - kfree(edit); -} - -/** - * assoc_array_gc - Garbage collect an associative array. - * @array: The array to clean. - * @ops: The operations to use. - * @iterator: A callback function to pass judgement on each object. - * @iterator_data: Private data for the callback function. - * - * Collect garbage from an associative array and pack down the internal tree to - * save memory. - * - * The iterator function is asked to pass judgement upon each object in the - * array. If it returns false, the object is discard and if it returns true, - * the object is kept. If it returns true, it must increment the object's - * usage count (or whatever it needs to do to retain it) before returning. - * - * This function returns 0 if successful or -ENOMEM if out of memory. In the - * latter case, the array is not changed. - * - * The caller should lock against other modifications and must continue to hold - * the lock until assoc_array_apply_edit() has been called. - * - * Accesses to the tree may take place concurrently with this function, - * provided they hold the RCU read lock. - */ -int assoc_array_gc(struct assoc_array *array, - const struct assoc_array_ops *ops, - bool (*iterator)(void *object, void *iterator_data), - void *iterator_data) -{ - struct assoc_array_shortcut *shortcut, *new_s; - struct assoc_array_node *node, *new_n; - struct assoc_array_edit *edit; - struct assoc_array_ptr *cursor, *ptr; - struct assoc_array_ptr *new_root, *new_parent, **new_ptr_pp; - unsigned long nr_leaves_on_tree; - int keylen, slot, nr_free, next_slot, i; - - pr_devel("-->%s()\n", __func__); - - if (!array->root) - return 0; - - edit = kzalloc(sizeof(struct assoc_array_edit), GFP_KERNEL); - if (!edit) - return -ENOMEM; - edit->array = array; - edit->ops = ops; - edit->ops_for_excised_subtree = ops; - edit->set[0].ptr = &array->root; - edit->excised_subtree = array->root; - - new_root = new_parent = NULL; - new_ptr_pp = &new_root; - cursor = array->root; - -descend: - /* If this point is a shortcut, then we need to duplicate it and - * advance the target cursor. - */ - if (assoc_array_ptr_is_shortcut(cursor)) { - shortcut = assoc_array_ptr_to_shortcut(cursor); - keylen = round_up(shortcut->skip_to_level, ASSOC_ARRAY_KEY_CHUNK_SIZE); - keylen >>= ASSOC_ARRAY_KEY_CHUNK_SHIFT; - new_s = kmalloc(sizeof(struct assoc_array_shortcut) + - keylen * sizeof(unsigned long), GFP_KERNEL); - if (!new_s) - goto enomem; - pr_devel("dup shortcut %p -> %p\n", shortcut, new_s); - memcpy(new_s, shortcut, (sizeof(struct assoc_array_shortcut) + - keylen * sizeof(unsigned long))); - new_s->back_pointer = new_parent; - new_s->parent_slot = shortcut->parent_slot; - *new_ptr_pp = new_parent = assoc_array_shortcut_to_ptr(new_s); - new_ptr_pp = &new_s->next_node; - cursor = shortcut->next_node; - } - - /* Duplicate the node at this position */ - node = assoc_array_ptr_to_node(cursor); - new_n = kzalloc(sizeof(struct assoc_array_node), GFP_KERNEL); - if (!new_n) - goto enomem; - pr_devel("dup node %p -> %p\n", node, new_n); - new_n->back_pointer = new_parent; - new_n->parent_slot = node->parent_slot; - *new_ptr_pp = new_parent = assoc_array_node_to_ptr(new_n); - new_ptr_pp = NULL; - slot = 0; - -continue_node: - /* Filter across any leaves and gc any subtrees */ - for (; slot < ASSOC_ARRAY_FAN_OUT; slot++) { - ptr = node->slots[slot]; - if (!ptr) - continue; - - if (assoc_array_ptr_is_leaf(ptr)) { - if (iterator(assoc_array_ptr_to_leaf(ptr), - iterator_data)) - /* The iterator will have done any reference - * counting on the object for us. - */ - new_n->slots[slot] = ptr; - continue; - } - - new_ptr_pp = &new_n->slots[slot]; - cursor = ptr; - goto descend; - } - - pr_devel("-- compress node %p --\n", new_n); - - /* Count up the number of empty slots in this node and work out the - * subtree leaf count. - */ - new_n->nr_leaves_on_branch = 0; - nr_free = 0; - for (slot = 0; slot < ASSOC_ARRAY_FAN_OUT; slot++) { - ptr = new_n->slots[slot]; - if (!ptr) - nr_free++; - else if (assoc_array_ptr_is_leaf(ptr)) - new_n->nr_leaves_on_branch++; - } - pr_devel("free=%d, leaves=%lu\n", nr_free, new_n->nr_leaves_on_branch); - - /* See what we can fold in */ - next_slot = 0; - for (slot = 0; slot < ASSOC_ARRAY_FAN_OUT; slot++) { - struct assoc_array_shortcut *s; - struct assoc_array_node *child; - - ptr = new_n->slots[slot]; - if (!ptr || assoc_array_ptr_is_leaf(ptr)) - continue; - - s = NULL; - if (assoc_array_ptr_is_shortcut(ptr)) { - s = assoc_array_ptr_to_shortcut(ptr); - ptr = s->next_node; - } - - child = assoc_array_ptr_to_node(ptr); - new_n->nr_leaves_on_branch += child->nr_leaves_on_branch; - - if (child->nr_leaves_on_branch <= nr_free + 1) { - /* Fold the child node into this one */ - pr_devel("[%d] fold node %lu/%d [nx %d]\n", - slot, child->nr_leaves_on_branch, nr_free + 1, - next_slot); - - /* We would already have reaped an intervening shortcut - * on the way back up the tree. - */ - BUG_ON(s); - - new_n->slots[slot] = NULL; - nr_free++; - if (slot < next_slot) - next_slot = slot; - for (i = 0; i < ASSOC_ARRAY_FAN_OUT; i++) { - struct assoc_array_ptr *p = child->slots[i]; - if (!p) - continue; - BUG_ON(assoc_array_ptr_is_meta(p)); - while (new_n->slots[next_slot]) - next_slot++; - BUG_ON(next_slot >= ASSOC_ARRAY_FAN_OUT); - new_n->slots[next_slot++] = p; - nr_free--; - } - kfree(child); - } else { - pr_devel("[%d] retain node %lu/%d [nx %d]\n", - slot, child->nr_leaves_on_branch, nr_free + 1, - next_slot); - } - } - - pr_devel("after: %lu\n", new_n->nr_leaves_on_branch); - - nr_leaves_on_tree = new_n->nr_leaves_on_branch; - - /* Excise this node if it is singly occupied by a shortcut */ - if (nr_free == ASSOC_ARRAY_FAN_OUT - 1) { - for (slot = 0; slot < ASSOC_ARRAY_FAN_OUT; slot++) - if ((ptr = new_n->slots[slot])) - break; - - if (assoc_array_ptr_is_meta(ptr) && - assoc_array_ptr_is_shortcut(ptr)) { - pr_devel("excise node %p with 1 shortcut\n", new_n); - new_s = assoc_array_ptr_to_shortcut(ptr); - new_parent = new_n->back_pointer; - slot = new_n->parent_slot; - kfree(new_n); - if (!new_parent) { - new_s->back_pointer = NULL; - new_s->parent_slot = 0; - new_root = ptr; - goto gc_complete; - } - - if (assoc_array_ptr_is_shortcut(new_parent)) { - /* We can discard any preceding shortcut also */ - struct assoc_array_shortcut *s = - assoc_array_ptr_to_shortcut(new_parent); - - pr_devel("excise preceding shortcut\n"); - - new_parent = new_s->back_pointer = s->back_pointer; - slot = new_s->parent_slot = s->parent_slot; - kfree(s); - if (!new_parent) { - new_s->back_pointer = NULL; - new_s->parent_slot = 0; - new_root = ptr; - goto gc_complete; - } - } - - new_s->back_pointer = new_parent; - new_s->parent_slot = slot; - new_n = assoc_array_ptr_to_node(new_parent); - new_n->slots[slot] = ptr; - goto ascend_old_tree; - } - } - - /* Excise any shortcuts we might encounter that point to nodes that - * only contain leaves. - */ - ptr = new_n->back_pointer; - if (!ptr) - goto gc_complete; - - if (assoc_array_ptr_is_shortcut(ptr)) { - new_s = assoc_array_ptr_to_shortcut(ptr); - new_parent = new_s->back_pointer; - slot = new_s->parent_slot; - - if (new_n->nr_leaves_on_branch <= ASSOC_ARRAY_FAN_OUT) { - struct assoc_array_node *n; - - pr_devel("excise shortcut\n"); - new_n->back_pointer = new_parent; - new_n->parent_slot = slot; - kfree(new_s); - if (!new_parent) { - new_root = assoc_array_node_to_ptr(new_n); - goto gc_complete; - } - - n = assoc_array_ptr_to_node(new_parent); - n->slots[slot] = assoc_array_node_to_ptr(new_n); - } - } else { - new_parent = ptr; - } - new_n = assoc_array_ptr_to_node(new_parent); - -ascend_old_tree: - ptr = node->back_pointer; - if (assoc_array_ptr_is_shortcut(ptr)) { - shortcut = assoc_array_ptr_to_shortcut(ptr); - slot = shortcut->parent_slot; - cursor = shortcut->back_pointer; - } else { - slot = node->parent_slot; - cursor = ptr; - } - BUG_ON(!ptr); - node = assoc_array_ptr_to_node(cursor); - slot++; - goto continue_node; - -gc_complete: - edit->set[0].to = new_root; - assoc_array_apply_edit(edit); - edit->array->nr_leaves_on_tree = nr_leaves_on_tree; - return 0; - -enomem: - pr_devel("enomem\n"); - assoc_array_destroy_subtree(new_root, edit->ops); - kfree(edit); - return -ENOMEM; -} |